1. Field of the Invention
The present invention relates to an image forming apparatus having a pair of fixing rotary members for fixing an unfixed image and a cleaning member for cleaning surfaces of the fixing rotary members.
2. Related Background Art
Conventionally, in an electro-photographic copying machine or printer, a thermal fixing system in which an unfixed sheet is passed through a pair of heated and pressured rollers has commonly been used. A heat-resistive releasing lubricant layer such as silicone rubber or fluoride resin from molten toner is provided on the surfaces of the rollers and other releasing lubricant such as silicone oil is applied to the surfaces to prevent the offset. Nevertheless, offset toner accumulated on the surfaces of the rollers deteriorate the rollers, so that the life thereof is shortened.
To solve this problem, cleaning is commonly performed by forced friction with a fibrous web pad to remove the offset toner from the surfaces of the rollers. The rollers, oil and cleaning member as consumption member are normally exchanged by a service man or a user one to several times during a lifetime of the apparatus.
Particularly, in a full color image forming apparatus, it is necessary to fix a thick toner layer of multi-color including yellow, cyan, magenta and black. An output close to a solid image not only a line image is required. As a result, a durability load is significantly large in comparison of a mono-color or dicolor system. Further, since those toners must be perfectly in a fused and mixed condition in order to enhance color development and color mixing, the toner resins used should be soluble sharply at a relatively low temperature and have a small viscosity. Such resin has a much poor releasing property from the rollers than that of mono-color material.
Accordingly, in order to maintain the releasing effect in the roller having a silicone rubber of fluoride resin surface, it is necessary to cover the surface with silicone oil to impart the releasing effect to prevent the offset phenomenon and the deterioration of the roller.
It has been contemplated to reduce the amount of oil used as much as possible to save manpower for exchange, reduce the size of an oil tank and simplify the application mechanism, but still it is troublesome to exchange the rollers and the web, and it is very difficult for the user to do it by himself.